A case-control study of hypertensive and normotensive oral contraceptive pill users from an Atlanta clinic was undertaken to determine the following: (1) if the blood levels of ethinyl estradiol (EE) are higher in hypertensive than in normotensive pill users; (2) if EE blood level declines at a different rate between the groups; (3) and to determine the relationship between EE blood levels and blood pressure. Thirty-nine cases (hypertensive oral contraceptive users) were recruited from the Atlanta Hypertension study. Twenty-four matched, and 104 unmatched controls were recruited from a nearby family planning clinic. It was found that EE levels in hypertensive OC users do not differ significantly from levels in normotensive users. The data does suggest however, that blood levels may decline somewhat more slowly among hypertensive than among normotensive OC users. Also, EE blood levels may correlate with the severity of high blood pressure among hypertensive OC users.